(α).
With verbs which designate going, coming, moving, bearing, bringing near, adapting, taking, receiving, calling, exciting, admonishing, etc., when the verb is compounded with ad the prep. is not always repeated, but the constr. with the dat. or acc. employed; cf. Rudd. II. pp. 154, 175 n. (In the ante-class. per., and even in Cic., ad is generally repeated with most verbs, as, ad eos accedit, Cic. Sex. Rosc. 8: “adSullamadire,” id. ib. 25: “adseadferre,” Cic. Verr. 4, 50: “reticulumadnarīssibiadmovebat,” id. ib. 5, 27: “adlaboremadhortantur,” id. de Sen. 14: “T. Vectiumadsearcessit,” Cic. Verr. 5, 114; but the poets of the Aug. per., and the historians, esp. Tac., prefer the dative; also, when the compound verb contains merely the idea of approach, the constr. with ad and the acc. is employed; but when it designates increase, that with the dat. is more usual: accedit ad urbem, he approaches the city; but, accedit provinciae, it is added to the province.）—

A. Form. According to the usual orthography, the d of the ad remains unchanged before vowels, and before b, d, h, m, v: adbibo, adduco, adhibeo, admoveo, advenio; it is assimilated to c, f, g, l, n, p, r, s, t: accipio, affigo, aggero, allabor, annumero, appello, arripio, assumo, attineo; before g and s it sometimes disappears: agnosco, aspicio, asto: and before qu it passes into c: acquiro, acquiesco.—But later philologists, supported by old inscriptions and good MSS., have mostly adopted the following forms: ad before j, h, b, d, f, m, n, q, v; ac before c, sometimes, but less well, before q; ag and also ad before g; a before gn, sp, sc, st; ad and also al before l; ad rather than an before n; ap and sometimes ad before p; ad and also ar before r; ad and also as before s; at and sometimes ad before t. In this work the old orthography has commonly been retained for the sake of convenient reference, but the better form in any case is indicated.—

B. Signif. In English up often denotes approach, and in many instances will give the force of ad as a prefix both in its local and in its figurative sense.